The specific accumulation of yolk proteins by the oocyte is a cornerstone of egg maturation and, therefore, a key element of reproductive physiology. The research proposed here concerns the elucidation of the molecular mechanism governing this process. We have generated a library of monoclonal antibodies against yolk protein at different processing stages in the mosquito oocyte. This gives us a powerful tool to analyse the mechanism of yolk accumulation and develop specific molecular probes. Purified vitellogenin (VG) will be labeled with radio-, fluorescent, and EM markers, and then used for binding and structural studies of its receptor. I intend to investigate the role of hormones and other factors in yolk accumulation. Radioligand binding assay will be used to determine the affinity and number of VG receptors on the oocyte membrane as well as the influence of various factors on these characteristics. I will study the nature of VG epitopes responsible for its recognition by the oocyte. Also, I propose to develop a probe specific for mosquito clathrin, a major component of coated vesicles, and then to study the developmental aspects of their biogenesis. I wish to determine: (1) when both VG receptors and clathrin are synthesized, and (2) what factors govern their production. An understanding of the VG-receptor system will set the stage for our next goal, purification and study of the molecular properties of the VG receptor. Information on the nature of VG recognition and its accumulation by the oocyte, as well as factors affecting this process, will provide an essential background in the search for new approaches in the control of this important arthropod vector.